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Heretaunga Plains Rivers Scheme
Right up to recent years the Heretaunga Plains of Hawke’s Bay have been subject to flooding – not just surface water from local rains, but major flooding from three of the six main rivers that enter the bay – the Tutaekuri, Ngaruroro and Tukituki Rivers. Although two of the worst floods occurred in 1867 and 1897 before back-country hills were entirely denuded of bush, the clearing of land for grazing has certainly not helped the plains area with its flood problems. However, since the Rivers Board, and later the Catchment Board, have been formed, the control of these three rivers has been less a matter of chance.
Now, the Catchment Board is completing the scheme which should protect the Heretaunga Plains from any further floods, such as… the 1935 flood pictured opposite. At that time hundreds of acres were inundated when the Tutaekuri flooded in the lower reaches. At that time there was no overflow channel for the adjoining Ngaruroro River.
In the diagram below, the Catchment Board has outlined the changes to be made.
1. Redesign Tutaekuri banks to take 100,000 cusec. flood.
2. Divert Tutaekuri to form common mouth with Ngaruroro.
3. Redesign overflow banks to take full flood flow of Ngaruroro of 160,000 cusec.
4. Divert Ngaruroro completely into its overflow channel.
5. By double banks, discharge flood waters of Tutaekuri Waimate into the system by gravity.
6. Extend road and railway bridges by approximately 400 feet.
7. Construct new bridge at Pakowhai over Ngaruroro, 1100 feet.
8. Retain existing channel of discharge for free discharge of Karamu and Raupare streams, draining 200 square miles.
9. Install pump station to drain 2600 acres of Pakowhai – Waiohiki area.
10. Install pump station to drain 2300 acres of Brookfield – Awatoto area.
11. Karamu Stream floodgates to be removed.
12. Remove bank between Tutaekuri and overflow to use existing Tutaekuri bridges as outlet for excess floodwaters.
The reasons for making these sweeping and costly changes in our river system are also made clear by the board. At present neither the Tutaekuri nor the Ngaruroro is capable of maintaining an open mouth to the sea, on its own. The re-alignment of the two rivers so that they combine about three-quarters of a mile inland will give a much stronger flow aimed more directly at the beach. The Tutaekuri, from Brookfields to the sea, loses flood capacity through silting up; the Pakowhai area becomes flooded when floodgates are closed on the Tutaekuri – Waimate; the Ngaruroro also tends to silt up from Pakowhai to the sea; the area served by the Karamu Stream and its tributaries – an area of 200 square miles including Hastings and Havelock North – becomes flooded when floodgates are closed at the junction with the Ngaruroro. This latter area will benefit greatly from the proposed scheme. Not only will the Karamu Stream have free outflow into the existing Ngaruroro riverbed but £160,000 will also be spent on improving the Karamu and its tributaries.
The whole scheme spread over four years will cost in the vicinity of £620,000, of which local ratepayers will have to find approximately £180,000.
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